The present invention relates generally to a novel odor sorbing packaging material and more particularly to a method for preparing such a material that can be converted into packages for products which generate objectionable odors.
One of the most widely accepted materials used to absorb odors is activated carbon. Activated carbon is used in paperboard packaging, filters, gas masks and other devices to absorb and trap objectionable odors, aromas and other impurities. For example U.S. Pat. Nos. 5,540,916 and 5,693,385, owned by the present assignee herein, disclose an odor sorbing packaging material comprising paperboard onto which there is applied a coating comprising activated carbon. Other prior art which discloses paper-based packaging containing activated carbon includes U.S. Pat. No. 2,593,146 which discloses laminated sheets for wrapping foodstuffs, and U.S. Pat. No. 3,149,023 which discloses treated paperboard for packaging. U.S. Pat. No. 4,504,290 discloses a filter element which contains activated carbon for odor control; U.S. Pat. No. 4,517,308 discloses the use of activated carbon in filter mats, air fresheners, inner soles for shoes etc.; U.S. Pat. No. 5,022,553 discloses a diaper storage container having a substantially rigid inner liner containing activated carbon; and, U.S. Pat. No. 5,860,391 discloses the use of activated carbon in animal litter. However, as will be noted, in each of the prior art teachings, the activated carbon applications have been made primarily to rigid or semi-rigid products. Accordingly, it is an object of the present invention to incorporate activated carbon into a non-rigid structure in an expeditious, economical and effective manner.
The present invention relates generally to packaging materials and more specifically to a substantially flexible packaging material that has been treated to absorb the odors and aromas given off by products contained within packages constructed from the packaging material. For this purpose, the present invention employs activated carbon, a material well known for its ability to absorb objectionable odors. In a preferred embodiment, the activated carbon is applied to one or both surfaces of a flexible, polymeric film material using conventional technology. However it is contemplated that other flexible substrates such as paper onto which there is applied a polymer coating, or laminates of paper and polymer films could be used.
Activated carbon materials such as the NUCHAR products sold by Westvaco Corporation (the assignee herein), are available in particle sizes, or can be ground to particle sizes, which are readily dispersable in coatings, inks or the like suitable for application to flexible film materials such as polyolefins. After application of the activated carbon to the film materials, the treated film can be converted into packages, liner elements, trash bags, pouches, wrappers or the like suitable for use in many different applications where odor absorption is desired.
It is therefore, an object of the present invention to provide an improved method for applying an odor sorbing coating to packaging material.
It is another object of the invention to provide an odor sorbing packaging material with a sufficient concentration of activated carbon to accomplish the purpose of deodorizing substantially the entirety of packages converted from the packaging material.
And, finally, it is an object of the invention to provide an substantially flexible odor sorbing packaging material that may be converted into various packages useful for a variety of purposes which require odor control.
To satisfy these and other objects of the present invention contemplates the use of activated carbon dispersed in a binder that can be applied to a polymeric film. Sub-micron carbon black is known for use as a coloring pigment in the manufacture of polyethylene resins to produce black trash bags. However, attempts to use typical odor sorbing activated carbons of larger particle size (5-40 microns) have been unsuccessful because the presence of the particles have produced films with holes (voids) at higher carbon concentrations, or low odor sorbing capacity at low carbon concentration. Likewise, attempts to apply an aqueous coating containing activated carbon to a polyolefin film have been less than successful. Such attempts have produced, on the one hand, coatings with a low carbon content (less than about 60%), that adhered well, but performed poorly in odor tests, or coatings with a carbon content greater than about 80%, with good odor sorption characteristics, but poor adhesion and excessive carbon rub-off. To overcome these problems, the present invention was developed. The present invention solves the problems referred to hereinbefore by applying the activated carbon containing coating in two steps.